1. Field of the Invention
The present invention relates to a separated-blade type shutter apparatus.
2. Description of the Related Art
There are two types of a conventional focal plane shutter which includes a parallel link mechanism made up of two arms to support group of a plurality of divided blades pivotably, constructed in such a way that pivoting of these arms causes the blade group to run between a superposed state and a spread state; a long-arm type and short-arm type depending on the different methods of holding the blade group by the arms.
Here, a so-called longitudinally moving focal plane shutter that moves the blade group up and down will be explained.
First, as disclosed in Japanese Utility Model Publication No. 35-29651, a long-arm type shutter apparatus includes blade group supported by the arms pivotably at locations on the opposite side of the arm base ends across the shutter aperture. Thus, the arms are longer than the width of the shutter aperture.
Such a long-arm type shutter apparatus needs only a small arm turning angle for opening/closing the shutter aperture by the blade group, reducing the amount of displacement of the blade group by the opening/closing operation in the direction orthogonal to the blade running direction, which is advantageous to a reduction of the horizontal width of the shutter.
However, increasing the number of blades of the blade group that can be supported by the two arms to 3 or more has a disadvantage of complicating the structure and a disadvantage in a high-speed movement because of the use of a long arm, which increases inertia of the blade unit.
For this reason, with the enhancement of the shutter exposure speed and strobe tuning speed in recent years, a long-arm type shutter apparatus unfit for speed enhancement is falling into disuse.
On the other hand, a short-arm type shutter apparatus proposed to cover the disadvantages of the long-arm type is constructed in such a way that a group of a number of blades are supported by two arms on the shutter aperture edge side near the base ends of the arms pivotably without sandwiching the shutter aperture, though it is disadvantageous to reducing the horizontal width.
Moreover, the lengths of the arms are often reduced to a minimum to further reduce inertia.
Examples of this short arm type are shown in FIG. 23 and FIG. 24. FIG. 23 shows a shutter apparatus ready to run and FIG. 24 shows the shutter apparatus, which has completed a running.
In these figures, reference numeral 101 denotes a board (shutter base plate) having a shutter aperture 101a. This base plate 101 supports base ends of a front shutter first arm 106 and a front shutter second arm 107 pivotably by axes 101d and 101e. 
The front shutter has a five-blade configuration and is constructed of a slit-forming blade 102 formed to open or close the shutter aperture and covering blades 103, 104, 105 and 105xe2x80x2. The slit-forming blade 102 and covering blades 103-105, 105xe2x80x2 are connected to the arms 106 and 107 pivotably by means of blade swaging dowel pins 108a, 108b, 108c, 108d, 108e, 109a, 109b, 109c, 109d and 109e, thus forming a parallel link.
Furthermore, this base plate 101 supports the base ends of a rear shutter first arm 114 and a rear shutter second arm 115 pivotably by axes 101f and 101g. The rear shutter has a four-blade configuration and is constructed of a slit-forming blade 110 formed to open or close the shutter aperture and covering blades 111, 112 and 113. The slit-forming blade 110 and covering blades 111-113 are connected to the arms 114 and 115 pivotably by means of blade swaging dowel pins 116a, 116b, 116c, 116d, 117a, 117b, 117c and 117d, thus forming a parallel link.
The swaging dowel pins of both the front shutter and rear shutter are positioned in sequence so as to draw a gentle arc and when the blade unit is in a superposed state to open the shutter aperture, the first arm and second arm are designed to align close to each other.
Furthermore, the external size of the blades for the front shutter necessary to secure an amount of overlapping among the adjacent blades for shielding when the blades are spread (here, equally 4 mm) and necessary to shield the shutter aperture is a little larger than the shutter aperture (here, approximately 2 mm in the vertical direction of the aperture and approximately 6.6 mm at the ends of the blades) considering an unnecessary increase of the blade inertia, (hereinafter, this shutter apparatus will be referred to as xe2x80x9cfirst conventional examplexe2x80x9d).
Furthermore, Japanese Utility Model Publication No. 53-39472 discloses a shutter apparatus in a configuration that the slit-forming blade is supported by a parallel link of relatively long type arms and opening/closing of the other covering blades is driven by actions of action pins and cum grooves.
In order to form the cum grooves for drive, the covering blades are shaped in such a way that the part near the blade root protrudes toward a position away from the shutter aperture when the blades for shielding the shutter aperture are spread, (hereinafter, this shutter apparatus will be referred to as xe2x80x9csecond conventional examplexe2x80x9d).
Furthermore, according to the shutter apparatus disclosed in Japanese Patent Publication No. 60-3165 (hereinafter, referred to as xe2x80x9cthird conventional examplexe2x80x9d) and the shutter apparatus disclosed in Japanese Utility Model Publication No. 7-25787 (hereinafter, referred to as xe2x80x9cfourth conventional examplexe2x80x9d), a protruding shape is formed near the root close to the coupling with the arm of the covering blade with the shortest running distance.
Furthermore, according to the shutter apparatus proposed in Japanese Patent Laid-Open No. 2000-180916 specification (hereinafter, referred to as xe2x80x9cfifth conventional examplexe2x80x9d), a shielding mechanism is provided between an image-taking lens and focal plane shutter and this shielding mechanism is provided so as to freely move between an open position at which the exposure aperture is exposed by superposing the upper two of the four shields above the exposure aperture and a shielded position at which the exposure aperture is shielded by spreading the shields so as to shield the generally upper half of the exposure aperture.
Moreover, the rest of the shields are provided so as to freely move between an open position at which the exposure aperture is opened by superposing the shields below the exposure aperture and a shielded position at which the exposure aperture is shielded by spreading the shields so as to shield the generally lower half of the exposure aperture.
When the user opens the back cover of the camera, the exposure aperture is doubly covered with both the blades of the focal plane shutter and the shield of the shielding section in that order from the back side (user side). The shields, which move a smaller distance, are provided with a protruding section to be connected using an arm and pin respectively so as to be located outside the exposure aperture in a shielded state.
With a camera incorporating the above-described focal plane shutter, there is a possibility that the user may touch the blades when opening the back cover and loading a film. In the case where the user touches the blades a little stronger, the blades may penetrate the shutter aperture causing the inconvenience of disabling the camera from taking images.
For example, in the above-described first conventional example, when the back cover of the camera is opened, since the front shutter covering the shutter aperture gives priority to the alleviation of inertia while maintaining the shielding performance, the front shutter does not have a shape strong enough to hold on when pressed by a finger, etc. from the back cover and may easily penetrate the shutter aperture.
Furthermore, when generally attempting to reduce the size of the shutter, reduce the horizontal width in particular, reducing the number of the divided blades of the blade group can reduce the number of connections between the arms and blades and thereby reduce the area occupied by the connected parts, which is advantageous to a reduction of the horizontal width.
However, reducing the number of blades of the blade group also reduces the amount of overlap among the blades to shield the shutter aperture of a predetermined size, making it difficult to secure the shielding performance.
Furthermore, since it is not possible to reduce the width per one blade so much, reducing the number of blades is disadvantageous to a reduction of the size in the height direction when the shutter top end located above the shutter aperture is brought closer to the shutter aperture.
In the above-described first conventional example, when the arms are shortened for miniaturization, since there are as many as five front-shutter blades, distances among the blades are reduced with the blade swaging dowel pins remaining arranged as they are, which reduces the degree of freedom of the support positions at which the covering blades can freely turn, and thereby causes interference inside the blade unit (for example, in FIG. 24, interference between the circumference of the base end 106b of the first arm 106 and the second arm 107 peripheral to the blade swaging dowel pin 109e or the circumference of the covering blade 105xe2x80x2 or interference between the circumference of the first arm 106 peripheral to the blade swaging dowel pin 108e and the second arm 107 peripheral to the blade swaging dowel pins 109c and 109d and the circumference of the covering blades 104 and 105, etc.).
For this reason, it is not possible to increase the arm rotation operating angle (since the size of the shutter aperture in the blade running direction is fixed, if the arm of a parallel link is shortened, it is necessary to increase the arm rotation operating angle to move the blade a predetermined distance) and it is also difficult to maintain the amount of overlapping between the slit-forming blade and the covering blades when the blades for closing the shutter aperture are spread, which makes it impossible to achieve significant miniaturization.
On the contrary, when the rear shutter in a four-blade configuration is also used for the front shutter commonly, the amount of overlapping among the blades when the rear shutter is spread is as small as approximately 2 as shown in FIG. 24. And even if the width of each blade is widened within the allowable blade housing space in the superposed state in which the front shutter opens the shutter aperture, distances among the blades are reduced with the blade swaging dowel pins remaining arranged as they are just like the above-described 5-blade configuration, which reduces the degree of freedom of the support positions at which the covering blades can freely turn because of the restrictions on the positions of the blade swaging dowel pins, and thereby causes interference inside the blade unit (for example, in FIG. 23, interference between the circumference of the base end 114b of the first arm 114 and the second arm 115 peripheral to the blade swaging dowel pin 117d or the circumference of the covering blade 113 or interference between the circumference of the first arm 114 peripheral to the blade swaging dowel pin 116d and the second arm 115 peripheral to the blade swaging dowel pin 117c and the circumference of the covering blade 112, etc.).
For this reason, it is only possible to widen by 1 mm in the opposite direction of the blade running direction, not possible to secure the amount of blade overlapping of desired 4 mm and nor possible to reduce the size so much (for an explanation of locations of the blade swaging dowel pins, see xe2x80x9cf.xe2x80x9d which will be described later).
Moreover, in the above-described second conventional example (Japanese Utility Model Publication No. 53-39472), since the blade drive arm is long, if the arm happens to be pushed when the shutter blade is pressed by a finger, etc. from the back cover side, not only this arm can hold on but also the protruding shape near the root of the cum groove forming blade of the covering blade can hold on a little more.
However, even in the vicinity of the center of the shutter aperture, if the arm is not pushed but the covering blade is directly pushed, the blade end side cannot hold on, and therefore the end of covering blade easily penetrates the shutter aperture.
In addition, the configuration that opening/closing of the parallel link of the relatively long type arms and the covering blades is controlled by actions of the action pins and cum grooves has a more complicated structure than a general parallel link mechanism with two arms as in the case of the first conventional example, also increases operating resistance and increases inertia of the blade unit.
Thus, the above-described second conventional example is disadvantageous for high-speed movement and can hardly realize an exposure time shorter than, 1/4000 sec or strobe tuning time shorter than 1/200 sec with a camera, for example.
Furthermore, the shutter charge energy necessary to realize the same shutter speed increases and thereby causes the size of the camera to increase, which is inconvenient for increasing a frame speed during continual picture taking.
Furthermore, in the above-described third conventional example (Japanese Patent Publication No. 60-3165) and fourth conventional example (Japanese Utility Model Publication No. 7-25787), the holding-on of the root of the blade slightly increases when the shutter blade is pushed by a finger, etc. from the back cover side (the blade root side can sufficiently hold on because high rigidity arms are originally provided on the blade root side), whereas the blade end side cannot still hold on sufficiently, and therefore the end of the covering blade can easily penetrate the shutter aperture.
Furthermore, in the above-described fifth conventional example (Japanese Patent Laid-Open No. 2000-180916), when the holding-on against a pressure is considered from the standpoint of the shape of the shield, if the shield is pushed by a finger, etc. from the back cover side when the exposure aperture is closed, since the shield root side is provided with high rigidity arms and these arms overlap with the protruding section of the shield, and therefore the holding-on against the pressure of the shield hardly changes irrespective of whether this protruding section is present or not, the shield root side can originally hold on in its own way.
However, since the shield end side cannot still hold on, the end of the shield easily penetrates the exposure aperture. That is, the protruding section of the shield is formed simply for the pin connection with the arms of the shield after all.
It is an object of the present invention to provide a shutter apparatus capable of increasing resistance to penetration by the blades while reducing an increase of inertia of the blade unit.
Furthermore, it is another object of the present invention to provide a shutter apparatus having a small size in the direction orthogonal to the blade running direction, capable of securing a sufficient amount of overlapping for blades, with high operating efficiency and suitable for high-speed operation.
In order to attain the above-described objects, the shutter apparatus of the present invention includes:
a base plate having a shutter aperture formed therein;
a plurality of blades which run between a superposed state and a spread state for opening and closing the above-described shutter aperture; and
two arms, each of the arms pivotably supported on the base plate and each of the two arms pivotably connected to the plurality of blades. The two arms cause the plurality of blades to run between the superposed state and the spread state, and
a protruding section is formed in a central area of at least one of the plurality of blades.
The protruding section protrudes in the blade running direction so as to overlap with the base plate in the spread state.
Furthermore, the shutter apparatus of the present invention includes:
a base plate having a shutter aperture formed therein;
a plurality of blades which run between a superposed state and a spread state for opening and closing the shutter aperture; and
two arms, each of the arms pivotably supported on the base plate, and each of the two arms pivotably connected to the plurality of blades. The two arms cause the plurality of blades to run between the superposed state and the spread, and
a protruding sectionxe2x80x94is formed in a central area of the blade which runs the shortest distance between the superposed state and the spread state out of the plurality of blades.
The protruding section protrudes in the blade running direction so as to overlap with the base plate in the spread state.
In the case where the shutter apparatus of the present invention includes a plurality of front shutter blades running from the spread state to the superposed state and a plurality of rear shutter blades running from the superposed state to the spread state after the front shutter blades start to run. The protruding section can be formed on the front shutter blade located closest to the end side in the blade running direction in the spread state or on the front shutter blade which runs the shortest distance between the superposed state and the spread state out of the plurality of front shutter blades.
Furthermore, the present invention are applicable to a so-called short arm type shutter apparatus wherein the arms are connected to the vicinity of the ends, on the base end side of the arms, of the blades.
Furthermore, a plurality of the protruding sections can also be formed on at least one of the plurality of the blades.
Then, the shutter apparatus of the present invention can be used for image-taking system of a camera and for shielding external light when writing images of an image display apparatus using storing/displaying device represented by a spatial light modulation element.
A detailed configuration of the shutter apparatus, of the invention, the above and other objects and features of the invention will be apparent from the embodiments, described below.